I'm sure you all must have heard of the XScale CPU. It was created by Intel until 2006 then that line up was sold by Intel. Intel said they sold the XScale so that they can focus on x86 chipsests like desktop, mobile and server CPUs only.

The Xscale was made for handheld devices where as the Atom is a full-fledged x86 CPU, which enables it to run software’s just like computers; it also supports Windows. The XScale processors use the ARM architecture.

If you try to use XScale in a typical computer, it won't boot up. The Xscale is a very good CPU for handheld devices i.e. MP3 players; the operating system of such device are mormally home-programmed, so they do use ARM architecture.

UMPCs uses native x86 instructions same as required to run Windows. I don’t thinkMicrosoft to make changes in Windows because of Xscale CPUs, and also the fastest are running around 600 MHz.